Miner left college after the 1992 season and declared himself eligible for the 1992 NBA Draft. He was selected by the Miami Heat with the draft's 12th overall pick.

Miner won the NBA Slam Dunk Contest twice, in 1993 and 1995. In the 1995 contest, Miner defeated Isaiah Rider, who had won the previous year, solidifying Miner as one of the game's best dunkers. However, his playing career proved unremarkable and failed to live up to the high expectations with which it began. Despite his dunking prowess, Miner did not get much playing time from Heat coaches, Kevin Loughery and Alvin Gentry.

I always felt the worst thing to happen to Harold was the "Baby Jordan" tag.

After the 1995 season, Miner was traded to the Cleveland Cavaliers. He averaged only 3.2 points and 7.2 minutes per game for the Cavaliers. On October 18, 1995 he was traded to the Toronto Raptors for Victor Alexander, but that trade was rescinded 4 days later when Alexander failed his physical. Miner played five scoreless minutes in his last NBA game, a 26-point loss to the Chicago Bulls on February 20, 1996.

Cleveland waived Miner, having played him in only 19 games that season. He tried out for the Toronto Raptors the following year but was cut during the preseason. Rather than continue to pursue a career in professional basketball, either in the NBA or overseas, Miner retired from the sport. He later said that his decision was prompted by the many knee injuries he suffered during his career.

As of 2011, Miner had settled in Las Vegas, Nevada, and was married with two children. He said that he had invested wisely the money he had earned in salary and endorsements during his playing career, allowing him to remain a stay-at-home father, rather than needing to seek employment. Over most of the time since his retirement from basketball, he had been disinclined to give interviews or make public appearances, instead remaining private and largely inaccessible. In 2010, however, he agreed to an interview in which he indicated a desire to begin reconnecting with the University of Southern California and with some of his acquaintances from his playing days.

In 2011, Miner appeared at the Pacific-10 Men's Basketball Tournament, to be inducted into that conference's basketball Hall of Honor, and indicated he planned to attend the retirement of his jersey by USC later that year. He would later attend the retirement of his jersey by USC during half time of the game against UCLA on 15 Jan 2012. Miner tied his previous seclusion largely to his disappointment with his professional career. Explaining his public reemergence, he said, "I guess I feel like I'm over it now. I've kind of purged my system and come to a point of accepting what happened with my career: that I wasn't able to live up to my own personal expectations."